Felt product and process therefor



May 7, 1957 P. s. Hess FELT PRODUCT AND Paocsss THEREFOR Filed Dec. 17. 1954 b/ m@ O .mv-11H30 OP INVENTOR PAU 1 s. H E 5 5.

BY Q. MMM 9,

ATTORNEY sumers.

subsequently may be laminated to the felt.

United States atent FELT PRODUCT AND PROCESS THEREFOR .Pn1ll.;less, Westrange, N. J., assignor to Congolenm- Nairn Inc., Kearny, N. J., a corporation of New Yori;

Application December 17, 1954, Serial No. 475,950

l12 Claims. (Cl. 92-3) This invention relates to strengthening agents for cellulosic bers in felted form and in particular, to new prodfuets which are suitable for -such use, Vand to .the processes for preparing and incorporating them.

Felted cellulosic fibers impregnated with 'bituminous materials yare frequently employed in the resilient door and -wa'll covering industry as a backing for linoleum, vinyl, printed felt base and the like. The felt is generally prepared .on conventional paper making equipment of the Fou-rdrin-ier or cylinder type. It is distinguished from paper in its thickness which ranges Vfrom about 0.025 inch to about 0.10 -inch and its gauge to Weight ratio which ranges from about 1.2 .to about 0.8 when measured by the .formula thickness of felt (inches) weight f .4.80 Sq. ft. of felt (pounds) Various types of felt may be prepared depending .on the source of the fibers which lare selected and the process of felting them. YSome felts employ 100% rags while .others maybe composed o-f 100% paper. Any combination of .cellulosic fibers may be used, and any given formulation of them as fed to a paper machine is called a furnish For .economic and other reasons, -it is impossible to `prepare `la -felt as .described above which has sufficient strength to function as a backing for -door and wall coveringproducts. `It has been `the practice therefore to ,provide .additional strength by impregnating .the `felt -with a .bituminous material, such as asphalt. Bitumen saturated felt is satisfactory for a great many purposes, but it also has certain disadvantages which the industry has .been seeking to overcome. -It tends to become .brittle when subjected tothe high temperatures :ordinarily encountered in processing. The color is unpleasing to many ,con-

The bitumen tends to migrate from .the `felt und consequently itis necessary to employ coating materials to prevent possible staining of a wear layer which Where very lhig'h `temperatures are required in processing, as in the case of laminatinga vinyl wear layer to a .saturated felt backing, problems .are encountered with blistering ldue to the saturant making it dillicult to obtain la smooth surface on either side of .the final product and more difficult to prevent staining.

`While substitutes for the bituminous impregnants have long been sought, only a few have reached the stage of being employed commercially. One such substitute ,comprises Va mixture of tall oil, |a plasticizer therefor, and an organic solvent. This mixture `has proved .objectionable for widespread use because it gives rise to a .great hazard of tire and explosion. The problem of solvent evaporation contributes to .this danger, but more importantly, there is a Klikelihood of spontaneous combustion due to the oxidation of the unsaturated aliphatic acids which are present. V'lfhe-mere drying and/or gelling of the mixiure after lithas been incorporated in felt at the required :temperatures of from about 180 F. -to about 200 F.

2,791,502 Patented May 7, 11957 has resulted in numerous tires. The stovinrg of linoleum which is blacked with such felt must be carefully conltrolled, and serious fires and explosions have occurred in .spite of the closest observation.

The present invention provides a lgreatly improved imvpregnant for door and wall covering felt. lt 4overcomes many of the disadvantages Iof bituminous impregna-nts and .permits the safe use Aof a .tal-,l oil compound.

Because it has been impossible to ascertain the precise chemical composition of vthe product of the present invention, it is described hereafter -in terms of the preferred process lof preparing it. Briefly stated, an ester of a polyhydric alcohol and tall oil is .oxidatively polymerized by heating it in .the presence of .excess oxygen until it has achieved a viscosityof from about 2,000ce11tip'oisesto about 10,000 icentipoisesaud thereafter itis further heated in .the absence of oxygen and at a vhigher temperature until Vit reaches a viscosity Vof at least about 30,000 centipoises, although it is not permitted to rea-ch a condition wllereafter gelling cannot be prevented. The oxidized and polymerized tall oil ester is then cooled to minimize further polymerization. A water emulsion of the above product may be prepared and the emulsion used ras an impregnant lfor felt in accordance with well-known techniques. 'It is usually desirable to cure or gel the impregant after it has been incorporated in the felt by subjecting it to elevated temperatures.

The product of the invention when used as a felt impreg-nant eliminates the problems of staining and makes unnecessary the use of expensive seal coats. lt provi-des a more attractive product lin that it has a lig-ht color, and it does not smear off when it brushes against furniture or the like during .handling and installation as does asphalt. It does not blister at high temperatures and therefore provides a smoother product when a vinyl wear layer is laminated .to it. In this regard, there is considerably less loss of goods in processing because when a vinyl product prepared in the usual way c'ontains too 4lmany and/or too large blisters, it is treated as waste.

A principal advantage of the product of vthe invention is its resistance to oxidation. lt is believed that the first step of the process; namely, the lox-i'dation of the tall toil ester to a condition ymeasured by u viscosity of between about 2,000 and 10,000 centipoises, elec-tsfoxidative polymerization of the ester by forming peroxides at the oxygen containing functional groups which in turn react with similar peroxide groups to form *oxygen linkages. The second step of the process apparently Veffects further polymerization by the creation of linka-ges between carbon atoms; it also destroys any unreacted peroxide groups. lf tbe second stage of polymerization .is not permitted .to reach a stage whereaft'er it is impossible to prevent gell'ing but does reach a degree of polymerization indicated by la viscosity :of at least about 30,000 centipoises, the product of the invention is lobtaineid which up'on coolingis water emulsiable and contains anumber of oxygen reactive groups small enough to eliminate any re or explosion hazard. On the .'ot-her hand, the product is strong enough for use as a felt impregnant. While the invention is not predicated on the above theory, it fis helpful by way of explanation in regard to the control lof the process.

The first stage of oxidative polymerization is best conducted at a temperature of below about 260 F. vand preferably at .about 210 F. At higher temperature, peroxide groups are destroyed too rapidly, thereby decreasing the number of voxygen linkages formed to a point below that necessary for achieving the product of the invention. Excess .oxygen must be supplied at the first o stage to permit the rapid formation of the peroxide Generally, the ester requires from about 4 to about 6 `hours to reach the desired viscosity, exclusive of the time :follow it byv a considerable period of time if the product of the first stage is kept at a low temperature on the order of below about 70 F. The diiiiculty with the latter procedure is that reaction, once started, continues to some extent at any temperature, and after a period of time the second stage of polymerization cannot adequately be controlled. In either event, however, the second stage is conducted in the absence of oxygen and preferably at a temperature of from about 520 F. to about 590 F. although any temperature is satisfactory if the aforementioned viscosity condition can be reached without gelation. At lower temperatures, the rate of carbon to carbon linking is slow and unreacted peroxide groups may not be destroyed. At higher temperature polymerization is too rapid to be satisfactorily controlled to prevent eventual gelling. It is preferable to pass carbon dioxide through the reaction vessel during the second stage to remove any water which is formed. It is also the best practice to cool the product when it has reached the desired viscosity during the second stage to prevent further reaction.

It has been found that the minimum viscosity of 30,000

centipoises required after the second stage of polymerization is important in providing a product which has the strength needed for use in lioor and wall covering felt. Any degree of polymerization represented by a higher viscosity may be used provided a substantial amount of gelling is not encountered prior to emulsification, but it becomes increasingly difficult to control the process in regard to gelling as the higher viscosities are sought. As the viscosity increases, the size of the combining molecules increases and each subsequent linking effects a greatly increased viscosity. In addition, subsequent emulsification becomes more diticult. For these reasons, it is preferred to maintain a viscosity in the second stage of polymerization below about 150,000 centipoises.

Emulsication of the product of the second stage of polymerization is easily accomplished, and it is preferred to employ an emulsifying agent such as morpholine, other amines, or the like. The emulsion may then be applied to felt by means of a coating apparatus or by dipping in a conventional manner, although it is usually desirable that the felt be supported during such an operation as it has a very low wet strength. Once the emulsion is incorporated in felt, it must be cured or gelled to provide the strength needed for iloor and wall covering products. The rate of gelling is accelerated by elevated temperatures and consequently their use is preferred. The proper degree of gelling `must be determined empirically and therefore no standard conditions of time and temperature can be set forth. Curing conditions of 250 F. for six hours followed by 180 F. for 2l days and 325 F. for 2 hours followed by 180 F. for 2l days have proved satisfactory. If a wear layer that requires stoving is to be laminated to the impregnated felt, all or a portion of the cure may be effected during stoving. Linoleum is generally stoved at temperatures of about 180 F. to 200 F. for from l0 to 30 days, and printed felt base is generally stoved for 2 to 5 days at the same temperaturcs. Preliminary curing prior to stoving or other treatment 'for from 30 minutes to 6 hours at temperatures ranging from about 180 F. to 325 F. is usually desirable in order to provide suilicient strength in the impregnatcd felt for handling and processing it. Where no stoving is intended, curing may be conducted at higher temperatures and the time required therefor is considerably decreased. Gelling apparently is a continuation of rise to the aforementioned tire and explosion hazard.

By conducting the second stage of the process 1n the absence of oxygen is meant simply that large amounts of oxygen are not permitted to be dispersed throughout the tall oil ester at this point. The reaction may be conducted in an ordinary reaction vessel which is exposed to the atmosphere, and the reactants may be agitated or stirred in the course of polymerization. A single reaction vessel may conveniently be employed for both stages of the process.

When using the product of the invention as a replacement for an asphalt impregnant, it has been found that about half as much of the modified tall oil ester based on the bone dry weight of the felt is required to achieve comparable strength, flexibility and stilfness values. For example, a product containing 120 parts of asphalt per 100 parts of felt has a tensile strength after 21 days of stoving, as measured by the Scott test, of 175. The Mullen bursting strength is 220 and the tear strength measured by the Thwing-Albert machine is 5.8. The flexibility as measured by the Mandrel test is onerhalf inches and the stiffness measured by the Suvant apparatus is 350. A product which is identical, except that 60 parts of the modied tall oil ester of the invention per 100 parts of bone dry felt is employed instead of the asphalt, has a Scott of 173; a Mullen of 225; a Thwing- Albert reading of 4.8', a Mandrel reading of one-half inch; and a Suvant of 225. The above tests are Well known, being used by a number of manufacturers of impregnated felt products to ascertain the indicated characteristics.

It is generally undesirable to use more than about of the modified tall oil ester of the invention in relation to the amount of bituminous material that ordinarily would be used to obtain given properties. 1f excessive amounts are used, the felt becomes extremely stiff over relatively short periods of time, and since the rate of stit'fening is accelerated by elevated temperatures, stoving accentuates the problem. For the usual type of oor and wall covering felts, the aforementioned amount of about 50% is most preferred although amounts as low as 25% provide felts suitable for speical needs.

Many tall oil esters of polyhydric alcohols are suitable as starting products in the present invention. Tall oil is obtained as a by-product in the manufacture of sulfate pulp from pine trees, and it contains varying amounts of rosin acids, drying oil fatty acids and unsaponiable matter depending on its source and the degree of refining it has undergone. American refined tall oil is generally preferred in the practice of the invention. Esterification of tall oil with a polyhydric alcohol is a well-known reaction; however, the ester referred to herein is that of the polyhydric alcohol and the fatty acids present in tall oil, there being no, or little, esterification of the rosin acids. This product is sometimes called a half ester.

The polyhydricalcohol employed in the esten'tication must contain at least three reactive hydroxy groups. If it contains less, the ester cannot be modified as described herein to provide sulcient strength for use in floor and wall covering felt. Pentaerythritol, which contains four reactive hydroxyl groups, is most preferred. Although glycerol esters have proved satisfactory for certain uses, they have less strength when used as an impregnant than do the most preferred pentaerythritol esters. Moreover,

y the glycerol esters require more time in processing, particularly during the second stage of polymerization, and take a longer time to completely gel after impregnation. The modification of tall oil esters of polyhydric alcohols having more than four hydroxyl groups results in stilerfinal products and are more ditlicult to control in preparation. Where stiffness is not a serious problem, as in a' backing material for tile, a tall oil ester of sorbitol may be used.

A process for preparing the product of the invention Y is set forth at Fig. 1 of the drawings and a detailed example of a preferred embodiment of the invention is described hereafter in connection therewith. The tall oil used fin preparing :the .ester `is American Arefined tall oil containing 68% fatty acids of which 36.5% is linolenic acid, 19% is linoleic acid and 43.7% is oleic acid; 30% rosinacids; and 2% unsaponiable matter. The tall oil is reacted with a stoichiometr-ic arnountof technical pentaeiythritol with reference to the -amount of fatty acids which are present, and the ester or half ester is thereafter separated. In the present example, 1000 pounds of the ester are introduced to the reaction vessel 1 which is heated by means of a steam 4jacket .(.not shown) to a temperature of 212 F. About 30 minutes are required for the ester to reach the desired temperature. Oxygen is passed through the reaction vessel Vfrom the time the ester is introduced. The amount of oxygen is suilicient provided it is being evolved lfrom `the reaction vessel. r[he reaction .is .allowed to continue for 4 hours at 212 F. at which time it has a viscosity of 5,000 centipoises as measured by a Brookfield Viscometer. The ester is then passed to reaction vessel 2 which is heated by a steam jacket (not shown) to 570 F. and CO2 is continuously passed through the contents of the vessel. After 2 vhours the ester reaches a temperature of 570 F. and after 30 minutes a viscosity of 30,000 vcentipoises as measured by a Brookeld Viscometer. The .ester is then quickly passed to a `cooling chamber 3 where it is reduced in temperature to `below 212 F. It is emulsied at 4 by adding 4 parts of morpholine and 100 parts of water for each 100 parts of modified tall oil ester. It is then stored at 5 until needed. The container 5 may be at room temperature.

When the modified ester is to be fused as an impregnant for felt, as shown in Fig. 2, it is removed from storage at 5 and passed to a dip tank 8 at a rate suicient to keep the tank adequately supplied. A previously prepared 100% cotton rag felt containing about 4% moisture is fed from a roller at 6 to a conveyor 7 where by 4means of roller `9 it is immersed vin dip tank 8. The felt remains in the dip tank for 0.05 second after which it has a moisture content of 50% based on the bone dry weight of the felt. Thereafter it is passed through an air heated chamber 10 where the moisture is substantially completely removed. The impregnated felt is then heated at 200 F. for 3 hours. It has a final modied tall oil -pentaerythritol ester content of 60% and the aforesaid strength, llexibility and stiifness characteristics as well as the other desirable properties herein discussed. At no point in the process is there -a iire or explosion hazard and the same do not exist with regard to any subsequent use which is made of the product.

While the above invention has been described in connection with specific and detailed examples, it is not to be limited thereby. Modiications and variations intended to be within the scope of the invention will be apparent to those skilled in the art and therefore reference is to be had to the appended claims for the limits of the scope of the invention.

What is claimed is:

1. A process for modifying an ester of tall oil, said ester containing free rosin acids in substantially the amount supplied by the tall oil, the fatty acid content of said ester being substantially completely esteried with a polyhydric alcohol having at least three hydroxyl groups, which comprises the steps of: first, heating the ester at a temperature of less than 260 F. in the presence of excess oxygen until it has a viscosity of from about 2,000 to about 10,000 centipoises; second, heating the product of the first step in the absence of oxygen until it has a viscosity of at least about 30,000 centipoises, said viscosity also being less than that at which gelling of the ester will occur; and third, cooling the product of the second step to a temperature of less than about 210 F.

2. A process for modifying an ester of tall oil, said ester containing free rosin acid in substantially the amount supplied by the tall oil, the fatty acid content of said ester .being substantially completely esteriedwith apoly- ,hydric alcohol |`having `at least three hydroxyl groups, which comprises the v`steps of: first, `heating the ester at a temperature less than about 260 F. in the presence of excess oxygen until `it has a viscosity `of from about 2,000 to about 10,000 centipoises; second, heating the product of the iirst step at a temperature within the range .of from .about 520 to vabout 59.0 F. fin the absence of ester being substantially completely :esteriiied with a polyhydric alcohol having at least three hydroxyl groups, kwhich Ycomprises `the steps of: first, heating the `ester at a temperature ,of less than 260 F. in the presence of `excessoxygen--until eithas a-viscosity of from about 2,000 to about 10,000 centipoises; second, heating the product of :the `first step in the absence :of oxygen until it has a viscosity of at 'least about 30,000 centipoises and vless .than 150,000 centipoises, said viscosity also 'being vless than that at which gelling of `.the ester Ywill occur; l'and third, cooling the product of the second step to a temperature of less than about 210 5. The process `of claim -4 Iwherein the heating in the presence .of excess oxygen is carried out for a period of about four to six hours.

6. The nprocess of vclaim -5 wherein the -polyhydric a-l- .cohol is pentaerythritol.

7. A liquid composition suitable `for impregnating felt and :which ycan be converted ,to a solid material by Vthe application of heat which comprises an ester of tall oil having .a 'viscosity .of from about 30,000 to about 150,000

centipoises, said 'ester -containing free rosin acid in substantially the amount supplied bythe tall oil and the yfatty acid content of said ester 4being substantially completely esteried 'with la polyhydric alcohol jhaving at least three 'hydroxyl groups, said ester having been preliminarily heated,atatemperature of'less than260 F. in the presence of oxygen 4until it "had a viscosity of from vabout 2,000 to about 10,000 centipoises and thereafter heated inthe Iabsence of oxygen -to 'increase its viscosity.

8. An emulsion suitable for impragnatiug felt which is converted to a solid residue by the application of heat which comprises water and dispersed therein an ester of tall oil having a viscosity of from about 30,000 to about 150,000 centipoises, said ester containing free rosin acid in substantially the amount supplied by the tall oil and the fatty acid content of said ester being substantially completely esterified with a polyhydric alcohol having at least three hydroxyl groups, said ester having been preliminarily heated at a temperature of less than 260 F. in the presence of oxygen until it had a viscosity of from about 2,000 to about 10,000 centipoises and thereafter heated in the absence of oxygen to increase its viscosity.

9. An emulsion suitable for impregnating felt which is converted to a solid residue by the application of heat which comprises water and dispersed therein an ester of tall oil having a viscosity of from about 30,000 to about 150,000 centipoises, said ester containing free rosin acid in substantially the amount supplied by the tall oil and the fatty acid content of said ester being substantially completely esterified with pentaerythritol, said ester having been preliminarily heated at a temperature of less than 260 P. in the presence of oxygen until it had a viscosity of from about 2,000 to about 10,000 centipoises and thereafter heated in the Iabsence of oxygen to increase its viscosity.

. l0. A ksheet of felted cellulosic bers having when dry a thickness of at least about 0.025 inch and less than about'O. l0 inch and a gauge to weight ratio of from about 0.8 to about 1.2 when measured by the formula felt thickness (inches) f weight of 480 square feet of felt (pounds) .about 30,000 to about 150,000 centipoises and containing free rosin acid in substantially the amount supplied by the tall oil and the fatty acid content of said ester being substantially completely esterilied with a polyhydric alcohol having at least vthree hydroxyl groups, said ester having been preliminarily heated at a temperature of less than 260 F. in the presence of oxygen until it had a viscosity of from about 2,000 to about 10,000 centipoises and thereafter heated in the absence of oxygen to increase its viscosity.

1l. A process for preparing a sheet of felted cellulosic bers impregnated with a strengthening agent which comprises depositing a slurry of loose cellulose fibers on a base in the form of a sheet and removing the moisture therefrom to provide a dry sheet having a thickness of at least about 0.025 inch and less than about 0.10 inch and a gauge to weight ratio of from about 0.8 to about 1.2 when measured by the formula applying a water emulsion of a modified tall oil ester to said dry sheet of felted bers, drying the sheet to resheet at an elevated temperature, said modied tall oil ester being prepared from a tall oil ester containing free rosin acids in substantially the amount supplied by the tall oil, the fatty acid content thereof being substantially completely esteriiied with a polyhydric alcohol having at least three hydroxyl groups, and said tall oil ester being modilied by iirst, heating the ester at a temperature of less than 260 F. in the presence of excess oxygen until it has a viscosity of from about 2,000 to about 10,000 centipoises; second, heating the product of the first step in the absenceof oxygen until it has a viscosity of at least about 30,000 ccntipoises, said viscosity also being less than that at which gelling of the ester will occur; and third,

`cooling the product of the second step to a temperature of less than about 210 F.

Y 12. A process for preparing a sheet of felted cellulosic fibers impregnated with a strengthening agent which cornprises depositing a slurry of loose cellulose fibers on a base in the form of a sheet and removing the moisture therefrom to provide a dry sheet having a thickness of at least about 0.025 inch and less than about 0.10 inch and a gauge to Weight ratio of from about 0.8 to about 1.2 vwhen measured by the formula felt thickness (inches) dipping said dry sheet of the felted libers in a Water emulsion of a modified tall oil ester, removing substantially all of the free moisture from the sheet and partially gelling the modified ester in the sheet by heating it at a temperature Within the range of from about 180 F. to about 375 F. for from about 30 minutes to about 360 minutes, said modified tall oil ester being prepared from a tall oil ester containing free rosin acids in substantially 'the amount supplied by the tall oil, the fatty acid content the'reof being substantially completely esteritied with pentaerythritol and said tall oil ester being modified by first, heating the ester at a temperature of about 210 F. in the presence of excess oxygen until it has a viscosity of from about 2,000 to about 10,000 centipoises; second, heating the product of the irst step at a temperature of about 570 F. in the absence of oxygen until it has a viscosity within the range of from about 30,000 centipoises to about 150,000 centipoises, said viscosity also being less than that at which gelling of the ester will occur; and

third, cooling the product of the second step to a tempera- 'turcof less than about 210 F.

move the water and gelling the modified ester in the ,Y

References Cited in the le of this patent UNITED STATES PATENTS V2,041,836 Hunt May 26, 1936 2,317,487 Schuelke Apr. 27, 1943 2,346,934 Miller Apr. 18, 1944 2,365,300 Segessemann Dec. 19, 1944 2,382,297 Cupery Aug. 14, 1945 2,424,074 Bent et al July 15, 1947 2,435,831 Harvey Feb, 10, 1948 2,447,506 Iubanowsky Aug. 24, 1948 2,493,486 Greenlee Ian. 3, 1950 2,494,559 Jubanowsky Ian. 17, 1950 2,516,104 Burrell July 25, 1950 

11. A PROCESS FOR PREPARING A SHEET OF FELTED CELLULOSIC FIBERS IMPREGNATED WITH A STRENGTHENING AGENT WHICH COMPRISES DEPOITING A SLURRY OF LOOSE CELLYLOSE FIBERS ON A BASE IN THE FORM OF A SHEET AND REMOVING THE MOISTURE THEREFROM TO PROVIDE A DRY SHEET HAVING A THICKNESS OF AT LEAST ANOUT 0.025 INCH AND LESS THAN ABOUT 0.10 INCH AND A GAUGE TO WEIGHT RATIO OF FROM ABOUT 0.8 TO ABOUT 1.2 WHEN MEASURED BY THE FORMULAR 